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post #31 of 47 Old 09-08-2016
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Re: Celestial Navigation

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Originally Posted by SkywalkerII View Post
I recently heard that the USN will once again teach CN at the academy after years.

Maybe cyber war back up?....
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So the only realistic way to actually loose every GPS signal on the boat would be if all the sattelites went down. But all those chips are multi-system ones. So it would take a shooting war between Russia, the US, and Europe, all of which would have to start the war by launching hundreds of sattelite killing missiles. To disable all of the major sattelite systems AT THE SAME TIME.

...
"Dithering: The introduction of digital noise by the DoD. The process by which the DoD used to add inaccuracy of GPS signals to promote Selective Availability".

They said it will not happen again. The ones who believe in this statement please raise their hands!

This is a real possibility any time they want the rest of the world to grind to a halt.

Even though Selective Availability only affect civilians, they are once again teaching Celestial. I got the message...
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post #32 of 47 Old 09-08-2016 Thread Starter
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Re: Celestial Navigation

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"Dithering: The introduction of digital noise by the DoD. The process by which the DoD used to add inaccuracy of GPS signals to promote Selective Availability".

They said it will not happen again. The ones who believe in this statement please raise their hands!

This is a real possibility any time they want the rest of the world to grind to a halt.
It's a good point, but would /could they ever make GPS as inaccurate as celestial?
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post #33 of 47 Old 09-08-2016 Thread Starter
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Re: Celestial Navigation

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[SIZE="4"][FONT="Verdana"]Yes on earth/ground/sea the Astronomic Navigation, is no more used/useful. But today the astronomic navigation, made by star-trackers, is the leading edge technology of the navigation for satellites and rovers!!!
Yes using small webcamera (known as CCD in Astronomic field) with fish-eye lens a program is able to understand where the craft is flying.

Also the GPS, using the shift of time signals, is based on the same concept of the Astronomical navigation.
Where is time of flight used in celestial?

On other planets / asteroids, we don't have orbiting GPS satellites, so have to use alternative means. Do you have any data on how accurate celestial is when automated with electronics?

Thanks,

Roger
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post #34 of 47 Old 09-08-2016
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Re: Celestial Navigation

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It's a good point, but would /could they ever make GPS as inaccurate as celestial?
Maybe, but the problem is that it may not be available everywhere for civilians, hence the need to learn as we may need to switch to plan B or C(elestial) for that matter.
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post #35 of 47 Old 09-08-2016
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Re: Celestial Navigation

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hence the need to learn as we may need to switch to plan B or C(elestial) for that matter.
As I stated above, learning celestial isn't a big deal, but it is useless if you don't use it often. Even someone very very proficient at it loses the knack after just a month or so of not using it several times a day, every single day.
Therefore, it is NOT a very good plan B or C or even Z as a back up for anything.

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post #36 of 47 Old 09-08-2016
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Re: Celestial Navigation

I checked with a friend of mine at the US Naval Accademy in Annapolis yesterday about them teaching CN again. He just laughed and said "Not a prayer!" He said that rumor has been going around for a decade or more, but it's just a rumor.

Gary
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post #37 of 47 Old 09-08-2016
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Re: Celestial Navigation

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Originally Posted by SVTatia View Post
"Dithering: The introduction of digital noise by the DoD. The process by which the DoD used to add inaccuracy of GPS signals to promote Selective Availability".

They said it will not happen again. The ones who believe in this statement please raise their hands!

This is a real possibility any time they want the rest of the world to grind to a halt.

Even though Selective Availability only affect civilians, they are once again teaching Celestial. I got the message...
Even assuming the DOD would introduce error, the degree of that error when it was last introduced was on the order of 1/4 mile. If you are good enough with celestial nav to get your error down to +\- 1/4nm you shall now be hailed as a god amongst men.

On the other hand even if the US DOD did introduce this error all modern GPS chip sets ALSO pull from the EU geolocation sattelites. So the DOD would need to also convince the EU to participate. Modern chip sets ALSO pull from the Russian geolocation sattelites so they would need to be on board as well.

Frankly if there is a global conflict so large that the US, EU, and Russia all are involved and feel the need to step down GPS locations I doubt that exact positional accuracy will be your major problem.

In the next few years, China will also be launching its own sattelite location system, and chip sets will add them to the mix.

It is almost absurd to envision a global conflict of such a nature that every major world power is involved, and yet my biggest concern is GPS accuracy to +/- 1/4nm versus the 50' I get now.

Edit: apparently I missed a few... India is launching a local system that covers the area from the Suez Canal East to Japan, and Japan is launching its own system as well.

Right now all major chip manufacturers can operate on at least the us-GPS, and the Russian-GLOSNAS system, and most of them can operate on the Chinese and EU systems as well.

Celestial navigation as a practical matter is dead and buried. Other than the oldest US sattelites no other positioning system is even possible of selectively degrading their accuracy. And the new gen systems are designed to provide accuracy to +\- 1m or better, with the EU and Chinese system designed for +\- 1cm.
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Last edited by Stumble; 09-08-2016 at 02:14 PM.
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post #38 of 47 Old 09-08-2016
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Re: Celestial Navigation

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Originally Posted by travlin-easy View Post
I checked with a friend of mine at the US Naval Accademy in Annapolis yesterday about them teaching CN again. He just laughed and said "Not a prayer!" He said that rumor has been going around for a decade or more, but it's just a rumor.
U.S. Navy Brings Back Navigation By The Stars For Officers

Reported by NPR on February 22, 2016

"In a big war, the GPS satellites could be shot down. Or, more likely, their signal could be jammed or hacked."

Catalina 22
on a starboard tack
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post #39 of 47 Old 09-08-2016
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Re: Celestial Navigation

My friend at the academy plays in the Navy Band, so maybe he does not have to worry about those navigation classes, but what the Hell do I know. Maybe he just skips those classses.

All the best,

Gary
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post #40 of 47 Old 09-08-2016
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Re: Celestial Navigation

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Originally Posted by Minnesail View Post
U.S. Navy Brings Back Navigation By The Stars For Officers

Reported by NPR on February 22, 2016

"In a big war, the GPS satellites could be shot down. Or, more likely, their signal could be jammed or hacked."
Yup... But in a war large enough to result in the destruction of all of the satellite navigation systems i doubt i will be cruising around the Carribean. The US Navy however still has to do its job.

Greg
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